When U.K. Prime Minister Boris Johnson announced in January that he would allow China’s largest telecom company to have a limited role in erecting a 5G wireless network for his country, the U.S. warned that there would be serious consequences.

President Donald Trump has now directed his administration to figure out exactly what they might be.

The National Security Council (NSC) this week launched an interagency review to determine what military and intelligence assets need to be removed from the U.K. if Huawei participates in building the 5G network, according to U.S. officials.

The dispute between the two allies comes down to whether a country can truly mitigate the intelligence threat posed by a Chinese company that has the ability to beam back data from its wireless network to the Chinese government.

Johnson has said the U.K. can, by barring Huawei equipment from base stations near sensitive military and intelligence sites and capping the company’s overall participation in the 5G network.

U.S. officials don’t believe these assurances.

As Secretary of Defense Mark Esper told Congress this week, "If our NATO allies incorporate Huawei technology, it may very well have a severe impact on our ability to share information, to share intelligence, to share operational plans and for the alliance to conduct itself as an alliance."

One senior U.S. official working on Huawei policy told me that one of the purposes of the interagency review was to take an inventory of U.S. equipment and bases in the U.K. and evaluate the risks of keeping them there. As this official said, the U.S. needs to assess the impact of "putting smart antennas and computers run by the Chinese Communist Party all over our closest ally."

Another source familiar with the review told me that the U.S. intention is not to punish the U.K. for letting Huawei into its 5G wireless network, but rather to take precautions against allowing China access to some of America’s most sensitive technology and secrets.

Whatever the intention, the U.K. has a lot to lose if the U.S. can no longer trust that its most sensitive intelligence and military programs can be protected from China’s prying digital eyes.

For example, the U.K. hosts the NSA’s largest overseas base at Menweth Hill, which was essential in combing through electronic data used by the U.S. military and CIA to target the locations of foreign terrorists.

According to a 2016 story in the Intercept, that base contains powerful antennae that can intercept signals between foreign satellites. It can also use U.S. satellites hovering above foreign countries to monitor wireless traffic below.

The Huawei decision has already disrupted some plans for basing U.S. equipment in the U.K. The U.S. is scheduled to send sensitive RC-135 surveillance planes to Royal Airforce Base Fairford by 2024. One Senate staffer told me these shipments may be on hold for now.

It’s not just in the U.S.’s interest to have this equipment in place — it’s also beneficial for the U.K. Especially with its departure from the European Union, the U.K. needs to maintain a high level of intelligence sharing with the U.S. for its own self-defense, given the long decline of its defense budget. And downgrading the U.S.-U.K. relationship now, in the face of a rising China, would signal a divided front against a potent adversary.

The good news for the U.S.-U.K. relationship is that the House of Commons still has an opportunity to reverse Johnson’s Huawei decision. Since Johnson’s announcement, a group of parliamentarians from his own party have rebelled against the government’s 5G plan.

If enough Tories break with their leader, there is a chance the U.K. can save itself from Johnson’s error — and in the process preserve their country’s most important alliance.

Eli Lake is a Bloomberg View columnist. He was the senior national security correspondent for the Daily Beast and covered national security and intelligence for the Washington Times, the New York Sun, and UPI. To read more of his reports,Go Here Now.